Closed system resistance units



Jan. 23, 1962 B. H. CLASON 3,018,457

CLOSED SYSTEM RESISTANCE um'rs Filed Jurie 22, 1959 2 Sheets-Sheet 1 IN VEN T OR.

Jan. 23, 1962 B. H. CLASON 3,018,457

CLOSED SYSTEM RESISTANCE UNITS Filed June 22, 1959 2 Sheets-Sheet 2 f i pi y INVENTOR.

Ai'ToRNEY United States Patent 3,018,457 CLOSED SYSTEM RESISTANCE UNITS Bertil H. Clason, Flint, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed June 22, 1959, Ser. No. 822,029 1 Claim. (Cl. 338-39) This invention pertains to units which vary in electrical resistance dependent upon fluid pressures encountered and more particularly-to units operable by pressures in closed fluid systems whereby current passing through the units is varied dependent upon those pressures to operate gages and the like.

An object of this invention is to provide an improved electrical resistance unit varying in resistance in accordance with fluid pressure in a closed system to which pressure the unit may be subjected and which unit will be simple in structure and reliable in operation.

A feature of the invention is a piston-operated electrical resistance unit in which the piston may be subjected to differential fluid pressures of two pressure zones in a closed fluid pressure system. Another feature is a resistance unit in which a piston is actuated by the differential pressures of two pressure zones in a closed fluid pressure system as supplemented by the potential force of spring means also acting upon the piston.

These and other important features of the invention will now be described in detail in the specification and then pointed out more particularly in the appended claims.

In the drawings:

FIGURE 1 is an end view of a portion of an automobile engine, much of that portion being in section better to illustrate one embodiment of the present invention.

FIGURE 2 is a diagrammatic representation of the electrical elements involved;

FIGURE 3 is an enlarged sectional view of a resistance unit as mounted on an engine as shown in FIGURE 1; and

FIGURE 4 is a sectional view looking in the direction of the arrows 4--4 in FIGURE 3.

In FIGURE 1, the engine generally indicated at is of the conventional V-type with an engine block 12, pistons 14 and a lubricating oil gallery 16 adapted to be supplied with oil under pressure.

The electrical resistance unit of the present invention is generally depicted at 20. This unit comprises a main body 22 in the form of a hexagonal member and a threaded neck portion 24 whereby the unit may be attached to the engine block 12. A portion 26 of the main body 22 is peened over to retain a dielectric or plastic housing 28, a washer 30 and a flange 32 tightly in position to form a unitary assembly. The flange 32 is held in an annular recess 34 formed within the body 22 and it is an integral part of a sleeve 36 which extends through the threaded neck portion 24. The latter is bored as at 38 to present an annular clearance around the shell 36. The washer 30 is interposed between the insulator housing 28 and the flange 32 and the material of this washer is resilient whereby the parts may be held permanently and tightly together.

The sleeve 36 has an annular series of perforations 40 near the flange 32 and these perforations communicate with a recess 42 formed within the body 22. At the other end of the sleeve 36, the latter is turned inwardly to form an annular shoulder 43 which defines a port 44. A piston 46 is slidably mounted within the sleeve 36 and a spring 48 is mounted between the shoulder 43 and the piston to act on the latter. A resilient conducting rod 50 extends from one end of the piston 3,018,457 Patented Jan. 23, 1962 46 to which it is aflixed and into a chamber 52 formed in the housing 28. This rod bears a metal contact ball 54 which is mounted in resilient engagement with at least one loop of a resistance coil 56 positioned within the chamber 52. The coil 56 is wound about a flat insulator strip 58 and is held1within a pocket 60 formed as an extension of the chamber 52 as best seen in FIG- URE 4. i I

' An electrical terminal 62 extends through the end wall of housing 28 and as the latter is of dielectric material, it is convenient to mold the terminal 62 in place in the housing when the housing per se is manufactured. The coil 56 is firmly held within the housing against endwise displacement by soldering or welding the same to a spring member 64 which in turn is pressed into position and into resilient contact with one end of the terminal 62. The sides of the chamber 52 will grip the spring member 64 and prevent displacement of the latter.

It will be noted that the engine block 12 is bored to form a passage 70 to accommodate the sleeve 36. It will be understood that the sleeve should tightly fit within the passage 70 preventing any undue communication between the oil gallery 16 and the interior space 72 of the crankcase.

It will be understood that the engine block 12 constitutes an electrical ground as shown in FIGURE 2 and that the terminal 62 is connected by means of a line 74 to a gage 76, the latter being conventional in being responsive to fluctuations in current. The gage 76 is also connected by a line 78 to a battery 80 and the battery in turn is grounded by a line 82.

In operation of the device, and assuming that the engine 10 is operating, it will be apprecitaed that the engine gallery 16 constitutes a zone of relatively high fluid pressure and this fluid pressure of the oil will be exerted by way of the annular clearance space 38, the recess 42 and the ports 40 against one end 84 of the piston 46. The other end 86 of the piston will be acted upon by the spring 48 and also by the atmospheric pressure of the crankcase as exerted through the port 44. As a consequence, the piston 46 will compress the spring 48 dependent upon the amount of oil pressure in the gallery 16 and the gage will register the pressure of the oil in the gallery by virtue of its pointer position. This is because the contact 54 will slide along the coil 56 to a position corresponding with the oil pressure in the gallery 16 and the resistance will accordingly be varied as the pressure varies. Oil leaking by the piston 46 will flow back into the engine crankcase by way of the port 44. The current will pass from the battery 80, through the gage 76 and the terminal 62 and then by way of a portion of the coil 56 as determined by the oil pressure and then by way of the contact 54, the arm or rod 50 and the piston 46 to the sleeve 36 and the engine block 12. The electrical resistance will increase as the pressure difierential increases and the gage will be calibrated accordingly.

Ordinarily it would be considered that a diaphragm could be used in place of the piston 46 but such is not the case. It would interfere with proper and sensitive actuation of the contact 54 necessary to secure accuracy for the gage 76. Loose free sliding of the piston 46 is accompanied by leakage around the latter but the system, being closed, permits return of the leaking oil to the crankcase without loss and free and reliable movement is definitely accorded the piston.

I claim:

A closed system resistance unit in combination with a support, the latter being adapted to serve as a ground and having two enclosed pressure zones, said unit including a body with threaded neck portion detachably secured to said support, a resistance coil located within said unit and insulated from said support, a terminal connected to one end portion of said coil, a piston slidable in said unit in a given path, a contact carried by one end of said piston and resiliently engaging said coil, spring means acting in said path against the other end of said piston, said unit further including a sleeve fixed within said body and slidably retaining the said piston and enclosing said spring means, said sleeve having perforations near one end, a passage in said threaded neck portion connecting one of said pressure zones by saidv perforations to said one end of said piston, a port at the other end of said sleeve connecting the other of said pressure zones to the said other end of said piston, and the arrangement being such that differential pressures 4 in said pressure zones acting against said piston may move the latter in said path and said contact along said coil to vary resistance to a current passing through said unit by way of said terminal, coil, piston and threaded neck.

References Cited in the file of this patent UNITED STATES PATENTS 462,837 Davis Nov. 10, 1891 1,341,542 Buchanan May 25, 1920 1,851,978 Dinger Apr. 5, 1932 2,621,274 Maddox Dec. 9, 1952 2,790,043 Clason Apr. 23, 1957 

